The present invention relates to the magnetic resonance arts, and more particularly to user interfaces for clinical imaging systems. The invention is particularly suitable for user interfacing with a magnetic resonance imaging (MRI) apparatus in a clinical setting, and will be described with particular reference thereto. However, it will be appreciated that the invention will also find application in conjunction with other MRI applications, other medical imaging methods and apparatus, in medical technologist training, and the like.
A magnetic resonance imaging (MRI) apparatus excites magnetic nuclear resonances in a subject, e.g. a patient, and manipulate and detect the resultant magnetic resonance signal. By limiting the spatial volume of the magnetic excitations and by spatially- and/or phase-encoding the magnetic resonance signal, usually through the use of applied magnetic field gradients, image representations of body parts, blood flow, injected radiopharmeceutical distributions, and the like are reconstructed from the magnetic resonance measurements.
MRI apparatus are operated in a multitude of imaging modes, for example SE, FE/CBASS, FSE, EPI (DWI/PWI), GRASE, and other modes. The choice of operating mode is based upon the body part to be imaged and the clinical aspects under study. By appropriately selecting MRI operational parameters the conditions can be selectively weighted to produce images that are proton density (xcfx81) weighted, T1, weighted, T2 weighted, et cetera. Scan parameters can also be optimized for imaging a particular body part and for using particular RF coils or coil arrays.
These various imaging capabilities are effectuated through appropriate selection of a large number of quantitative input parameters, such as the scan repeat time, the scan resolution, the interecho spacing, the bandwidth, the time-to-echo, and so forth. In all, twenty to forty input parameters are typically available for operator manipulation. These parameters are not, however, fully independent insofar as the setting of one parameter, e.g. the bandwidth, typically changes or limits the dynamic range of other parameters, e.g. the scan time.
The vast quantitative input parameter space often introduces practical limitations on the obtained image quality. Clinical MRI systems are usually operated by technologists who often have limited knowledge of the physical interrelations between the various parameters. Clinical MRI systems are also usually operated under significant time constraints in which patient throughput is an important consideration. Imaging under these conditions is often performed using sub-optimal parameter values, and these sub-optimized imaging conditions lead to degraded image quality that can limit the clinical value of the results. Thus, a critical area of clinical MRI development is the user interface design.
Prior art user interfaces (UI) typically provide the operator with a large number of input parameters, e.g. typically twenty to forty input parameters. Operator guidance in user selection of these parameters is usually limited to providing pre-designed parameter value sets for specific imaging tasks. Thus, for example, a technologist who wants to acquire a T2 weighted brain scan using an EPI imaging mode retrieves a pre-designed parameter value set corresponding to that type of image. The retrieved parameters are displayed by the UI. The operator typically either executes the scan using the pre-designed parameter values in unmodified form, or makes parameter adjustments through the UI based upon the operator""s prior experience and knowledge prior to acquiring the image.
In the latter case, the prior art UI systems usually provide only limited operator assistance in making the adjustments. Typically, feedback includes only a signal-to-noise ratio (SNR) value and a pixel or voxel size. A specific absorption ratio (SAR) value is usually calculated as a safety check, but the SAR user feedback is often limited to an overrange alarm indicator which indicates that the patient would be subject to unacceptably high energy fields during image scanning using the presently selected parameter values.
Importantly, the prior art UI systems typically provide no user guidance with respect to parameter interrelations and tradeoffs, beyond generally unhelpful parameter-out-of-range errors. In view of the demanding time constraints often imposed on clinical MRI, the technologist often finds these complex prior art UI systems overly complicated and contributory to operator errors and to sub-optimal acquired images. Only a limited amount of information about the interrelations which connect the MRI operational parameters is provided.
The present invention contemplates an improved system and method which overcomes the aforementioned limitations and others.
According to one aspect of the invention, a method for providing guidance to a magnetic resonance imaging (MRI) apparatus operator is disclosed. A desirability factor function is calculated, which depends upon a plurality of MRI operating parameters. Optimized values are obtained for the plurality of MRI operating parameters through analysis of the desirability factor function.
Preferably, the calculating of a desirability factor function includes calculating a monitor function, calculating a penalty function corresponding to a first parameter selected from the plurality of MRI operating parameters, and calculating the desirability factor function by mathematically combining the monitor function and the penalty function.
Preferably, the calculating of a monitor function includes calculating an estimated signal-to-noise ratio value. The mathematical combining preferably includes additively or subtractively combining the estimated signal-to-noise ratio with the penalty function.
The calculating of the penalty function preferably includes calculating a barrier function that has a prohibitively undesirable value within a pre-selected range of the first parameter.
The calculating of the penalty function preferably includes calculating a function whose value becomes less desirable as the value of the first parameter increasingly deviates from a default range.
The obtaining of optimized values for the plurality of MRI operating parameters through analysis of the desirability factor function preferably includes optimizing the desirability factor function with respect to at least one of the plurality of MRI operating parameters using an iterative optimization algorithm.
The obtaining of optimized values for the plurality of MRI operating parameters through analysis of the desirability factor function preferably includes graphically displaying a plot of the desirability factor function plotted against at least one of the plurality of MRI operating parameters on a display area of an associated interactive display device. A selection of the optimized values is received from the MRI apparatus operator via the associated interactive display device.
The method preferably further comprises: receiving initial values for the plurality of MRI operating parameters; calculating limit values corresponding to the MRI operating parameters; calculating values for a set of monitor parameters; displaying values of a sub-set of the MRI operating parameters; displaying the limit values for the sub-set of MRI operating parameters; and displaying the calculated monitor parameter values.
According to another aspect of the invention, a method for providing guidance to a magnetic resonance imaging (MRI) apparatus operator is disclosed. An operating curve is calculated indicating allowable combinations of values for a plurality of MRI operating parameters. An optimized combination of values for the plurality of MRI operating parameters is obtained by analyzing the operating curve.
Preferably, the obtaining of an optimized combination of values for the plurality of MRI operating parameters includes graphically displaying the operating curve on a display area of an associated interactive display device, and receiving a selection of the optimized combination of values from the MRI apparatus operator via the associated interactive display device.
According to yet another aspect of the invention, a magnetic resonance imaging (MRI) apparatus having a user interface (UI) system for interfacing with an associated user is disclosed. A means is provided for exciting a magnetic resonance. A means is provided for detecting the magnetic resonance. A display device and a user input device are provided. A processor cooperates with the user input device to receive values for selectable parameters that define an imaging sequence. The processor calculates minimum and maximum limit values for the selectable parameters, and also calculates values for a plurality of monitor parameter values. The monitor parameter values are determined by the processor based upon the selectable parameter values. A first display area on the display device identifies the values of a sub-set of the selectable parameters and the minimum and maximum limit values therefor. A second display area on the display device identifies the values of the monitor parameters. An interaction means operates in conjunction with the user input device, whereby the associated user selectively supplies a new value for one of the selectable parameters.
Preferably the processor calculates new values for the minimum and maximum limits and new values for the monitor parameters based upon the new value,.
The MRI apparatus preferably further includes a master database memory that contains at least one of a pre-designed sequence parameter values set, a previously run sequence parameter values set, information about previous magnetic resonance imaging sessions, and a historical customer database of sequences. The master database memory further contains sample images corresponding to the sequence parameters sets contained in the memory. A recall area on the display device displays an indication of the sequence parameter values sets stored in the master database memory along with at least one of the sample images.
The MRI apparatus preferably further includes a UI mode selector. The UI mode selector has an operational mode wherein the UI system operatively communicates with the means for exciting a magnetic resonance and with the means for detecting the magnetic resonance. The UI mode selector also has a training mode wherein the UI system does not operatively communicate with the means for exciting a magnetic resonance.
Preferably, the sub-set of the selectable parameters includes at least one of: a repeat time (TR), a resolution, an interecho spacing, a bandwidth, and a time-to-echo (TE). The monitor parameters preferably include at least one of: an estimated signal-to-noise ratio (SNR), a resolution, a scan time, a specific absorption ratio (SAR), a rate of magnetic field change (dB/dt), a T1 weighting, a T2 weighting, and a proton density weighting.
The second display area preferably includes a stacked bar having a first component indicating the estimated signal-to-noise ratio (SNR) and a second component indicating the rate of magnetic field change (dB/dt).
The second display area preferably includes a stacked bar having a first component indicating the T1 weighting, a second component indicating the T2 weighting, and a third component indicating the proton density weighting.
The processor preferably calculates a curve comprising one of a desirability factor function and an operating curve calculated as a function of a domain comprising at least one parameter selected from the selectable parameters. The second display area includes a graphical display of the curve. The interaction means operates in conjunction with the graphical display of the curve whereby the associated user selectively supplies the new value comprising an updated value for the domain.
According to still yet another aspect of the invention, a method is disclosed for providing guidance to a magnetic resonance imaging (MRI) apparatus operator. Limit values are calculated corresponding to selectable parameters. Values are calculated for monitor parameters. Values of a sub-set of the selectable parameters that govern the MRI apparatus operation are displayed. The limit values for the sub-set of the selectable parameters are displayed. The calculated monitor parameter values are displayed.
Preferably, the method further includes optimizing a desirability factor by adjusting at least one selectable parameter in accordance with a pre-defined mathematical optimization algorithm whereby the at least one selectable parameter is optimized.
The displaying of values of a sub-set of the selectable parameters that govern the MRI apparatus operation preferably includes displaying a value of a first selectable parameter on a slider. The displaying of the limit values for the sub-set of independent parameters includes displaying a limit value corresponding to the first selectable parameter on the slider. Preferably, the method also includes receiving a new value for the first selectable parameter by moving the slider, such moving being constrained by the limit value corresponding to the first selectable parameter.
Preferably, the method further includes plotting a curve comprising one of a desirability factor, a monitor parameter, and a selectable parameter, as a function of a domain comprising at least one selectable parameter.
Preferably, the method further includes obtaining a base function value, obtaining at least one penalty function value, normalizing the penalty function value, and calculating a desirability factor function by combining the base function value with the normalized penalty function value.
The calculating of values for monitor parameters preferably further includes normalizing a monitor parameter value with respect to a default value of the monitor parameter.
The method preferably further includes storing information about an imaging session in a data repository. The stored information can include at least one of an independent parameter value, a dependent parameter value, and an image. Selected contents of the data repository are displayed, and a selection of a stored imaging session from the user based on the displayed contents of the data repository is obtained. Initial values for the selectable parameters corresponding to the stored selected imaging session are retrieved from the data repository. Optionally, the data repository is remotely monitored and the stored imaging sessions analyzed to detect MRI apparatus defects or sub-optimum imaging conditions selected by the MRI apparatus operator.
One advantage of the present invention is that it provides a graphical user interface for adjusting a sub-set of the independent parameters that are most commonly accessed in clinical MR imaging.
Another advantage of the present invention is that it provides the user with a plurality of monitor parameters in a graphical display format such as a directed arrow, pie chart, bar graph, or the like.
Another advantage of the present invention is that it optimizes a selected set of parameters through iterative optimization of a defined desirability factor that depends upon the selected parameters.
Another advantage of the present invention is that it provides a data repository containing sample images corresponding to stored parameter sets to guide the user in selection of an appropriate stored sequence.
Yet another advantage of the present invention is that it provides a common interface for MRI clinical imaging and for operator training.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment.